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88355711 gastrointestinal physiology objectives answered

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Gastrointestinal Physiology
Section 1
Functions and Regulation of the GI Tract:
1. List the major organs within the GI system and overall functions of the GI system.
- GI tract: mouth, esophagus, stomach, small intestine, large intestine, rectum and anus
- Accessory glands: salivary glands, liver, gallbladder and pancreas
2. Differentiate between ingestion, digestion, absorption, metabolism, secretion, and
- Ingestion: take food into the body by swallowing or absorbing it.
- Digestion: process of breaking down food by mechanical or enzymatic action in the stomach
and intestines
- Absorption: pass into the body from the GI
- Metabolism: chemical process occurring within a body to maintain life
- Secretion: substances produces by cells or glands are moved into the GI
- Excretion: removal from the body.
3. Review histological features of the wall of the GI
- Four histologically defined regions:
o Mucosa: consists of single layer epithelium
that is highly folded. The epithelium is
frequently invaginated to form tubular
exocrine glands
o Submucosa: connective tissue layer with
major blood and lymph vessels. Also has
large number of ganglion cells forming the
Meissner’s plexus
o Muscularis externa: contains major smooth
muscle (peristalsis); inner circular and
outer longitudinal
o Serosa: thin connective tissue through which the major vessels and extrinsic nerve
4. Compare and contrast smooth and striated
muscle with respect to structure, excitation contraction coupling, and cellular
mechanism of contraction.
Comparison between Smooth and Straited Muscles.
- Cell bundles in SM have diverse orientations due to the lack of a discrete muscle origin and
- Contractile filaments are arranged irregularly (no sarcomeres) this allows force
generation over a wide range of muscle lengths (termed “length adaptation”). There are
large numbers of actin filaments attached to dense bodies and it is mainly through
interconnections of these dense bodies that the force of contraction is transmitted from cell
to cell.
- Smooth muscle contains both actin and myosin filaments. It does not contain the normal
troponin complex that is necessary in the control of skeletal muscle contraction.
- Contraction of smooth muscle requires conformational alteration of myosin head whereas
with striated muscle there is movement of the troponin-tropomyosin complex on the actin
- The Sarcoplasmic Reticulum is not organized into a T-tubule system. The caveoli which
represent invaginations of the smooth muscle membrane are analogous to T tubules in
striated muscle

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